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Robert Niebergall, Julio C. Martinez-Trujillo; Reference frames for covert spatial attention during smooth pursuit tracking of visual targets. Journal of Vision 2007;7(9):901. doi: 10.1167/7.9.901.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies have demonstrated that attention favors the processing of visual information at attended locations. However, it remains unclear the reference frame in which spatial attention operates. For example it is possible that attention selects object locations in an eye-centered frame of reference. This implies that when the eyes move (e.g., during smooth pursuit eye movements) targets that remain fixed in retinal coordinates will be better attended than other targets that move relative to the retina. On the other hand, it is also possible that in the same situation, we better attend to targets that remain fixed in space-coordinates, even if those targets are moving relative to the retina. To investigate this issue we tested human subjects' performance during an orientation discrimination task in which they pursued a fixation target and covertly attended to a target Sine-Wave grating that, a) remained fixed in eye-centered coordinates but moved in space-centered coordinates (eye-centered condition), and b) vice versa (space-centered condition). The horizontal, vertical and torsional eye movement components were measured during the task trials. Previous to the trials we obtained a measurement of the Listing's plane for each subject. We found that all subjects were able to accurately pursue the fixation target with eye movements following 3D trajectories that fitted their Listing's planes in both conditions. However, there was a bias toward larger deviations from the Listing's plane when targets remained fixed in space coordinates. Orientation discrimination thresholds in all subjects (n=3) were at least 2 times larger in the space-centered relative to the eye-centered condition. These results suggest that (i) covert attention tracks visual targets more efficiently in an eye-centered relative to a space-centered frame of reference and (ii) there may be a violation of Listing's law during attentional pursuit tracking of targets in space centered coordinates.
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